1. Field of the Invention
The present invention relates to a filter processing technique.
2. Description of the Related Art
Recently, digital cameras have achieved higher image qualities of more than 20,000,000 pixels, and can capture high-quality images at high resolution. However, while the user presses the shutter, the camera may shake or a blur may occur owing to the optical system or out-of-focusing. In this case, the image quality degrades and the advantage of high image quality cannot be fully exploited.
To improve poor image quality, there is proposed a method for recovering an image by applying, to the image, filters different between respective pixels (areas), such as a shake filter against camera shake, an optical filter corresponding to the image height of a lens, and a blur filter corresponding to the object distance (patent literature 1 (Japanese Patent Laid-Open No. 2005-63323)).
There is also proposed a method of holding not all filters different between respective pixels but only representative filters, and generating the remaining filters by linear interpolation (patent literature 2 (Japanese Patent Laid-Open No. 2005-31759)).
However, the method in patent literature 1 needs to hold all filters different between respective pixels and thus requires a large memory capacity. The method in patent literature 2 generates a filter between representative filters simply by linear interpolation. However, linear interpolation decides the weight based on the distance between filters. When the filter characteristic does not change depending on the distance, no intermediate filter can be generated at high precision. Also, the method in patent literature 2 can reduce the data amount of filters to be held, but cannot decrease the operation amount used when filters act on an image.